Codec Reference =============== This page summarizes the built-in field codecs. For constructor signatures and implementation details, see :doc:`python_api`. Numeric Codecs -------------- ``integer`` / ``varint`` Encodes an integer bounded by ``min_value`` and ``max_value`` using the number of bits required for that range. Values outside the configured range are clipped. ``fixedint`` Encodes an integer with an explicit ``num_bits`` width. Set ``signed`` to encode signed values. ``uint8``, ``uint16``, ``uint32``, ``uint64`` Fixed-width unsigned integer aliases. ``int8``, ``int16``, ``int32``, ``int64`` Fixed-width signed integer aliases. ``egint`` Encodes an integer with exponential-Golomb coding. This is useful when smaller values are much more common than large values. Floating-Point Codecs --------------------- ``float`` Quantizes a floating-point value between ``min_value`` and ``max_value`` with the configured decimal ``precision``. Encoded values are lossy and decode to the represented decimal value. ``linspace_float`` / ``linspace`` Quantizes a floating-point value into a fixed number of evenly spaced values between ``min_value`` and ``max_value``. Configure exactly one of ``resolution``, ``num_values``, or ``num_bits``. ``float32`` and ``float64`` Encodes IEEE 754 binary floating-point values with 32 or 64 bits. These are less compact than quantized float codecs but preserve ordinary float semantics. Boolean, String, and Bytes Codecs --------------------------------- ``bool`` / ``boolean`` Encodes a Python boolean as one bit. ``string`` / ``ascii`` Encodes an ASCII string with a length prefix and a maximum configured length. Strings longer than ``max_length`` are truncated unless the codec is configured to fail on overflow. ``bytes`` Encodes bytes with a length prefix and ``max_length`` bound. ``string_enum`` Encodes one string selected from a configured set of allowed values. Container Codecs ---------------- ``dict`` / ``dictionary`` Encodes a nested Python dictionary using a nested ``fields`` mapping. ``msg`` / ``ros_msg`` Encodes a nested ROS message. ``ros_type`` identifies the message class, and ``fields`` can override or limit the fields encoded from that message. ``variable_len_array`` Encodes a list with a length prefix. ``max_length`` controls the largest representable list. ``element_type`` and ``element_params`` configure the element codec. ``fixed_len_array`` Encodes a fixed number of elements. The encoded bitstream does not include a length field, so the decoder always reads ``length`` elements. ``optional`` Encodes a boolean presence field. When true, the configured ``target_fields`` are encoded immediately after the presence bit. Special-Purpose Codecs ---------------------- ``pad`` / ``padding`` Reserves a fixed number of zero bits. Padding decodes to ``None``. ``time`` / ``rostime`` Encodes ROS time values with configured seconds and nanoseconds ranges. ``ccl_latlon`` and ``ccl_latlon_bcd`` Encodes latitude and longitude values using compact formats compatible with CCL-style acoustic messages. ``lzma`` Compresses a byte-oriented payload with LZMA before encoding it with a length bound. Metadata Codecs --------------- Metadata aliases such as ``src``, ``dest``, ``toa``, and ``snr_in`` are not ordinary payload codecs. They copy values between decoded messages and packet metadata. See :doc:`codec_aliases` for the complete alias table.